That's correct, Altix ICE (and Altix XE) are clusters. Each 2-socket node runs its own kernel,
and there is no shared memory between nodes, so inter-node communication is with message
AFAIK all big shared-memory machines SGI makes are Itanium-based.
I suspect the answer to this conundrum is that this changeset just increases some previous
x86-only max-cpu limit, and the mention of 4096-way machines refers to the Itanium-based SGI